This invention relates to pressure-sensitive record and transfer sheet material of the kind widely used in continuous and uni-set business forms, manifold books and credit transaction records. Visible records are formed in one or more copies by application of writing or printing pressure in the desired pattern with handwriting instruments, typewriters, embossed cards, printing plates, computer printers, or the like.
In making multiple copies of a record, transferable carbon has long been used both as individual sheets, either single use (one time carbon) or multiple use carbon papers, and as a permanent coating on the back of a record copy which transfers to an underlying sheet when writing pressure is applied. The original is often a ribbon copy.
Transferable pressure making record materials comprising coatings having a profusion of discrete liquid droplets of marking material dispersed in a pressure rupturable matrix are known and are disclosed for example in U.S. Pat. Nos. 2,374,862; 2,299,693; and 2,299,694. As disclosed therein, a wide variety of matrix materials and liquid droplets can be used. Dyes, pigments or mixtures thereof can be dissolved or dispersed in a carrier liquid, generally of relatively low viscosity and which can be either volatile or non-volatile, and the resulting dispersion emulsified into small droplets in a matrix of film forming material for coating. Also, mixtures of two color forming co-reactants separated prior to application of marking pressure can be employed. Encapsulated droplets can be formed by coacervation as disclosed for example in U.S. Pat. No. 2,800,457.
In U.S. Pat. No. 3,020,171 issued Feb. 6, 1962, a marking system is disclosed wherein the record marks are formed by rupturing liquid droplets of marking material and allowing the liquid to flow through the sheet to form a visible mark on the side opposite the coating. Such systems have the potential to mark two sheets at once, the top surfaces of the sheets below and above the droplets, thereby reducing the number of coatings required. So far as is known, however, the system has not been used commercially to any significant extent. This is believed to be due to lateral as well as vertical movement of the liquid marking material through the sheet producing a blurred image with loss of definition.